In periodontal therapy, pathologic pockets are frequently treated by scaling, curettage and flap surgery. Post-operatively, there is a risk of re-infection of these pockets thus jeopardizing healing and regeneration of the periodontal tissues. The objectives of this research are to evaluate several methods of plaque inhibition on the development of subgingival plaque and to determine the effect of dental plaque inhibition on the healing and regeneration of the periodontal tissues following treatment. An additional objective is the further development of an animal model to study subgingival bacterial colonization and periodontal treatment. In the first project, subgingival microbial colonization on mylar strips will be studied. Labrador dogs will have mucogingival flaps elevated, buccal bone removed mylar strips placed and the flaps replaced on all canines. They will receive three different post-operative treatments: (A) Chlorhexidine, (B) Oral Tetracycline, and (C) the combination of (A) and (B). After 28 days, the strips will be removed, dispersed and cultured to give a total bacterial count as well as anaerobic and aerobic counts. The relative effectiveness of the plaque inhibition methods will be determined. In the second part of the project, chronic standardized periodontal defects as well as furcation and circumferential defects will be treated with scaling and curettage, Widman flaps, and antibiotic irrigation. Post operatively, the experimental side will receive the optimum method of chemical plaque inhibition for 28 days while saline will be applied to the controls. The animals will be sacrificed and histometric and histopathologic evaluation of the healing and regeneration will be performed and analyzed statistically to determine the effect of post- operative subgingival plaque inhibition.